This invention relates to a microcrystal precipitation type Fe type soft magnetic thin film having a high saturation flux density. More particularly, it relates to a soft magnetic thin film having high performance and high reliability, and a magnetic head and a recording apparatus produced by using the soft magnetic thin film.
Needs for compact, and moreover, high density information storage apparatuses have been increasing with the recent progress of the high information society. To accomplish high density recording, a medium having a high coercive force so that very small recorded magnetic domains exist stably, and a high performance magnetic head capable of recording information to this medium are necessary. To record signals by magnetizing the medium having a high coercive force, a magnetic head material having a high saturation flux density and capable of generating a strong magnetic field is necessary. Fe--C type and Fe--N type materials are known at present as the materials having a high saturation flux density. These materials are thermally treated at a predetermined temperature so as to exhibit soft magnetic characteristics. The temperature of this thermal treatment is decided by a temperature necessary for exhibiting the soft magnetic characteristics (crystallization point). This temperature further depends on the materials employed and their composition. When a magnetic head is produced by using the materials, particularly when the head is a metal-in-gap (MIG) type head, annealing at a predetermined temperature is necessary because the head production process includes a glass bonding step. The bonding temperature in this case is determined by the material of fusing glass. The temperature is determined by the melting point of fusing glass and is ordinarily set to a temperature higher than the crystallization temperature. For, when the bonding temperature is high, the strength of glass becomes high and when the bonding temperature is low, on the contrary, the strength of glass becomes low. For this reason, the bonding temperature of glass used ordinarily is higher in most cases than the temperature at which the soft magnetic characteristics are exhibited. This means that the magnetic film must has thermal stability to withstand at least the melting point of glass used. Particularly because the soft magnetic characteristics depend on the size of the fine crystal particles that precipitate, the crystal particle size must be controlled in order to obtain a magnetic film having excellent soft magnetic characteristics.
Since these materials consist of Fe as the principal component, they react with oxygen in air or water and form hydroxides and oxides to thereby invite the fluctuation of the magnetic characteristics, particularly the coercive force and the saturation flux density. In consequence, performance of the magnetic head drops in some cases. To put the magnetic head using the materials into practical application, therefore, the fluctuation of the magnetic characteristics due to corrosion when the magnetic film is left standing in the environment of use must be restricted, and such a fluctuation must also be eliminated even after the magnetic head is passed through the glass bonding step.
To solve these problems, proposals have been made to add those elements which improve the corrosion resistance in addition to magnetic elements. Nonetheless, it has been difficult in the past to simultaneously satisfy the soft magnetic characteristics and the corrosion resistance. JP-A-03-20444 is one of the prior art references examining these technical points.
The prior art reference described above discloses a method which is effective for improving any one of the soft magnetic characteristics, thermal stability and corrosion resistance. However, the reference does not sufficiently disclose a method for improving simultaneously all these characteristics. The reference does not at all teach or suggest the method for simultaneously improving the characteristics for soft magnetic films having a saturation flux density of at least 1.5T.